Food patties of various kinds, including hamburgers, molded "steaks", fish cakes, poultry patties, pork patties, and various vegetable patties, are frequently formed in high volume automated molding machines. Patty molding machines successfully adaptable to any of these food products are described in Richards Reissue U.S. Patent Re. No. 30,096 reissued Sept. 18, 1979, Sandberg et al. U.S. Pat. No. 4,054,967 issued Oct. 25, 1977, and Lamartino et al. U.S. Pat. No. 4,182,003 issued Jan. 8, 1980.
Although any of those machines, and others as well, are capable of producing food patties of consistent size, weight, and configuration on a high volume basis, substantial problems may be encountered when the machines are required to mold patties from food products which, unlike hamburger, have not been ground to relatively small particle size. Thus, it may be desirable to form patties from a food product that has not been chopped or ground; the starting material may consist of whole poultry breasts, large segments of pork or other meat, large fish fillets, or relatively large pieces of almost any food product that has an appreciable fiber content. In this specification and in the appended claims, food products of this general kind are referred to as "fibrous food products".
A molding mechanism that solves many of the problems encountered in molding food patties from a whole fiber food product is described in Sandberg et al. U.S. Pat. No. 4,356,595 issued Nov. 2, 1982. In one form of that molding mechanism, which uses a plural cavity mold plate disposed in close-fitting relationship between planar surfaces of a fill member and a cover member, the food product is pumped into the mold cavities through aligned fill apertures in the fill member; the fill apertures are preferably matched in size to the mold cavities they serve. However, even that molding mechanism presents some technical problems in its operation when employed to mold patties from fibrous food products.
In a molding mechanism of this kind, the total clearance between the mold plate and the adjacent cover member and fill member is only about 0.001 inch to 0.003 inch (0.025 cm. to 0.076 cm.). When pumped into the mold cavities the food product is under high pressure; the pumping pressures may be 400 psi (28 Kg/sq.cm.) in the machine of the Richards patent, 220 psi (15.5 Kg/sq.cm.) in the mechanism of the Lamartino patent, and 250 psi (17.6 Kg/sq.cm.) in the Sandberg et al. U.S. Pat. No. 4,054,967. These high pressures tend to force the mold plate into firm contact with the cover member (usually a breather plate), leaving all of the available clearance as a minute space between the mold plate and the fill member. When the mold plates moves from its fill position toward its discharge position, fibers of the food product tend to be pulled into this very limited space between the mold plate and the fill member, trailing behind the mold cavity, creating an undesirable hinge effect at a later point in the mold plate cycle. Another problem in molding food patties from fibrous products occurs because large segments of the food product may tend to bridge parts of the fill member between fill apertures, so that the bridging food product segments are torn as the high pressure pumping action forces them through the fill apertures. These difficulties are effectively resolved in Sandberg U.S. Pat. No. 4,697,308, issued Oct. 6, 1987.
The Sandberg mechanism, U.S. Pat. No. 4,697,308, does an excellent job in molding patties from fibrous food products when the fill apertures are not substantially smaller than the mold cavities. For some food patties, however, it is better to employ food ports, immediately ahead of the mold cavities, that are substantially smaller in area than the mold cavities. For this situation, any of the known machines, including those referred to above, tend to cut the fibers in the food product along the rims of the food apertures, just ahead of the mold cavities. This can have a noticeable deleterious effect on the finished patties, particularly in appearance, an important consideration in any restaurant operation.